Hoses for air-driven dental handpieces are commonly of two types. One type is extruded from a relatively soft and flexible polymeric material and provides a multiplicity of connected parallel conduits for transmitting drive air, exhaust air, chip air, and water. One such commercially available hose provides four conduits for fluid transmission and, in addition, a fifth conduit which may contain a fiberoptic waveguide (for the transmission of light to an illuminator located at the head of a handpiece) or electrical leads (for transmitting electrical energy to a light source provided by the handpiece). A second type of hose consists essentially of a flexible outer tube, often cloth-covered, containing a plurality of separate conduits or conductors for air, water, light, and/or electricity.
Both types of hoses resist twisting with torsional forces that may be sufficient to present objectionable interference to certain manipulative actions of a handpiece in use. In an effort to minimize such restraints, and the spring-like torsional restoring forces that develop when twisting does occur, dentists commonly check to make certain that a substantial length of hose has been extended and is in an untwisted or neutral state as the instrument is moved into a position for cutting, polishing, or other function the dentist selects. Even so, limited rotation of the handpiece about its longitudinal axis as it is manipulated in use does tend to be restrained to a noticeable extent by a typical multiple-conduit hose, and, even more significantly and a more onerous and fatiguing load on the operator, the restoring forces continually exerted by such a hose when it is twisted may further interfere with handpiece manipulation.
Efforts to reduce such problems have included swivel couplings of the type disclosed in co-owned U.S. Pat. No. 3,173,207 and in patents 3,936,940, 3,894,338, 4,217,101, 2,442,033, 4,213,243, 4,251,212, and 4,303,392. All of such constructions achieve unlimited swivel action at the price of increased structural complexity and manufacturing costs. In general, such a swivel coupling typically consists of male and female elements with multiple longitudinal passages that are maintained in selective communication with each other by a plurality of radial passages and annular channels isolated by sealing rings.
This invention is concerned with a relatively simple swivel arrangement for dental handpiece hoses in which the resistance to handpiece rotation about its longitudinal axis, caused in part by the multiple conduits twisting about each other, and the restorative forces exerted by such a hose when so twisted, may be greatly reduced if, first of all, at least adjacent portions of such conduits are unattached to each other for a substantial stretch (generally at least three inches), so that such unattached portions may flex independently with respect to the other conduits and, second, if a plurality of such separate distal portions are provided with individual swivel connectors. In such a construction, when the handpiece hose is twisted so that the multiple conduits or conductors become coiled about each other, each conduit nevertheless rotates at its own swivel connection and, because of such separate swivel action and rotational freedom, the resistance to twisting is reduced, and even more important the restorative action of the hose is substantially eliminated. Therefore, and especially for handpiece rotations which are normally limited to less than one full turn in either direction, the hose construction of this invention constitutes a relatively simple, low-cost, and highly effective arrangement for reducing to a low level the twisting forces required to rotate the handpiece and to an insignificant level the torsional restoring forces that would otherwise develop as a hose is twisted during ordinary handpiece operation.
It has also been found that such improvements may be achieved in a dental handpiece hose where only the larger conduits (the term "conduits" being used herein to mean fluid-transmitting tubes as well as electrical and light transmitting lines) are equipped with swivels. In general, the conduits requiring individual swivels are those used for transmitting drive air, light, and exhaust air. Other tubes, such as those for chip air and coolant water, are relatively small in diameter and have relatively little torsional stiffness and spring-like effect. Since therefore a separate swivel connection for the water line has been found unnecessary, the problems of developing a low torque dynamic seal in a swivel connection for the water passage are avoided.
The swivel connectors for all fluid conduits have low torque characteristics (under 0.5 inch ounces, and preferably under 0.2 inch ounces) and self-energizing fluid seals. Such seals are adjustable during factory assembly by compressing the elastomeric sealing ring with a retainer collar until the desired balance between torque and sealing capability is achieved, it being recognized that small leaks of drive air or exhaust air to atmosphere may be unobjectionable.
In one embodiment of the invention, the multiple conduits are contained within an outer tube, the outer tube in turn being equipped with its own swivel coupling to the handle of a dental handpiece. Such swivel coupling, like the swivel connectors for the individual conduits contained within the outer tube, may be provided with a self-energizing seal, especially if the outer tube, which is substantially larger in diameter than all of the conductors extending therethrough, is utilized for the transmission of exhaust air. Also, such embodiment may include a helical spring or liner disposed within the outer tube to give shape retention to the cross-section and to prevent sharp bends and lumen constriction that might reduce the free swivel action of the separate conductors extending through that outer tube. A further modification of this aspect of the invention may include a corrugated or other outer tube which is bendable without flattening, without the use of a spring or liner.
Other features, advantages, and objects of the invention will become apparent from the specification and drawings.